1. Field of the Invention
The present invention relates to turbine rotors of turbines for industrial applications and a gas turbine having the turbine rotors.
2. Description of Related Art
The present invention is applied to turbines for industrial applications including a gas turbine and a steam turbine. Hereinafter, a description will be given of an example in which the turbine rotor of the present invention is applied to the gas turbine.
First, FIG. 7 shows a general structure of the gas turbine. In the gas turbine, air is compressed by a compressor 101, the thus compressed air is introduced into a combustor 102, a fuel is fed into the combustor 102 to generate a combustion gas, and the thus generated combustion gas is introduced into a turbine 103 to rotate the turbine for obtaining electricity from a generator 104.
In general, a turbine rotor is connected with a compressor rotor through an intermediate shaft for connecting both axes, such that they are driven coaxially trough the coaxial axis and driven coaxially.
The compressor rotor and the turbine rotor are both an assembly of rotor discs constituted by stacking disc-like rotor discs inline with an axial line direction of the rotor and fixing them by a bolt. That is, in the compressor rotor, respective blades of the disc-like rotor discs are mounted in a radial direction on the outer circumference and stacked in the axial direction of the rotor, and each of the rotor discs is integrally fixed by a spindle bolt that penetrates through the axial direction of the rotor. This structure is also the same as that in the turbine rotor. The structure is found not only in a rotor for the gas turbine but also in a rotor for the steam turbine.
As shown in FIG. 8, annular projected portions 52 arranged in a concentric manner with a rotor disc 50 are formed at a flat-plate like side-face portion 51 of the rotor disc 50. The projected portion 52 is approximately rectangular in the cross section, and the annular projected portion 52 is projected in parallel to the center axis of a rotor shaft. Further, the projected portion 52 is constituted with a central side face 53 facing the rotor shaft, an outer circumference side face 54 facing the outer circumference of the rotor disc 50 and a top face 55 that is in contact with an adjacent rotor disc (not illustrated). When a plurality of rotor discs 50 are stacked, with the centers thereof in alignment with each other, the top face 55 of the projected portion 52 is in contact with the top face of the projected portion of an adjacent rotor disc. Then, a spindle bolt (not illustrated) is inserted into a bolt hole 60a drilled in the rotor disc 50 to fasten a plurality of the rotor discs 50 integrally, by which the top faces of the projected portions are in press contact with each other by a fastening force of the spindle bolt.
Further, a plurality of grooves 33, the cross section of which is semi-circular, are formed on the top face 55 of the projected portion 52 at which the respective rotor discs 50 are in press contact with each other. At the time of assembling a turbine rotor and when one rotor discs is in contact with the adjacent rotor disc, the center of the groove 33 formed on the top face 55 in the radial direction of the projected portion 52 of one rotor disc 50 is aligned with the center of the other groove 33 formed on the top face 55 of the projected portion 52 of the other adjacent rotor disc 50, a cylindrical hole 35 penetrating through the top face 55 is formed in the radial direction by two projected portions 52 of a pair of top faces 55 which is in press contact with each other.
When the turbine rotor is assembled, a columnar torque pin 40 is inserted into the cylindrical hole 35. The torque pin 40 has functions to prevent adjacent rotor discs 50 from being disengaged in the rotational direction and the torque pin has a role to transfer a rotational torque from one rotor disc 50 to another adjacent rotor disc 50.
The torque pin 40 is provided with a cylindrical main body 41 and flanges 42, 43 attached on both ends of the main body 41 and the diameter of the torque pin 40 is greater than that of the main body 41. The flange 42 is arranged at the center of the rotor disc 50 to prevent the torque pin 40 from coming off in the radial direction due to centrifugal forces during operation. The flange 43 which is arranged on the outer circumference of the rotor disc 50, is to prevent the torque pin 40 from dropping down due to its own weight when the operation of the rotor is terminated.
Further, when an additional torque is applied to the turbine rotor 1 from one end thereof, the rotor blade assembly absorbs the torque corresponding to the additional load. In a case that the load is a generator, a torque which is several times higher than a rated load, is applied, and since a load (for example, a generator) is connected to the other end of the turbine rotor 1, the load must be absorbed by friction of top faces 55 of the rotor disc 50 and the torque pin 40.
It is necessary that all the torque pins 40 are fitted into the cylindrical holes 35 leaving no space. Therefore, after a plurality of rotor discs 50 are stacked and fastened by the spindle bolt 60 to fix the rotor discs 50 integrally, it is necessary to form a plurality of cylindrical holes 35 for connecting rotor discs for stabilization of respective rotor discs. Each cylindrical hole is formed extending two top face of the two top faces of a pair of projected portions 52 of a pair of adjacent rotor discs, the top faces 55 of the pair of adjacent rotor discs are in press contact with each other. Japanese Unexamined Patent Application No. 2001-3702 has disclosed in a specific manner an example of the above-described rotor disc.
However, in order to insert the torque pins 40 into the cylindrical holes 35 after formation of the cylindrical holes 35, it is necessary to disassemble a rotor which has been once assembled. In other words, the rotor is disassembled to separate adjacent rotor discs 50, to thereby the torque pins 40 are inserted into the grooves 33. Thereafter, the rotor discs 50 are again assembled and fastened by the spindle bolt 60, in order to integrate the rotor discs 50 into a single unit. As described above, the turbine rotor has to be disassembled and has to be reassembled, thus the assembly operation was complicated.
According to the invention disclosed in U.S. Pat. No. 6,287,079, as shown in FIG. 9, after a plurality of rotor discs are stacked and fastened into a single unit, circular holes 81 are formed between two projected portions of a rotor disc on which top faces 55 are pressed against each other. Thereafter, torque pins 70 can be inserted from the outside of the assembled rotor disc into cylindrical holes formed between two projected portions of the rotor disc, thereby it becomes possible to simplify the assembly of the turbine rotor by omitting one step of the assembly operation.
Specifically, circular holes 81 are formed at both projected portions of the rotor disc 50 on which the top faces 55 are pressed against each other, and the torque pins 70 are attached into the circular holes 81. A cam 72 attached to a main body 71 of the torque pin 70 is rocked at the center of a pivot pin 73 by pressing a dump bolt 74 and fitted into a groove 82 disposed on the circular hole 81 drilled on the rotor disc side. As a result, the rotor disc 50 and the torque pin 70 are kept engaged via the cam 72 and will not fall out even if a centrifugal force acts on the torque pin 70.
However, it is difficult to carry out machining operation for the above-described complicated structure. For example, It is necessary to drill a circular hole through an assembled structure, in which a plurality of the rotor discs 50 are fixed integrally and thereafter, to form the groove 82 in the small inner wall face inside the circular hole 81. It is quite difficult and also time-consuming to form the groove as described above. Further, in a structure in which the cam 72 rotates around the center of the pivot pin 73, the cam is likely to be heated and stacked by a high temperature atmosphere and may become made unworkable within a short time. It is, therefore, not always possible to guarantee the reliable operation.
An object of the present invention is to provide turbine rotors and a turbine in which the two-time assembly work of the turbine rotors can be avoided to greatly reduce the number of man-hours necessary for assembly. Another object of the present invention is to provide a structure which reduces the number of components and the number of steps in processing, and the number of man-hours necessary for assembly of turbine rotors, as well as to be capable of securing the operation, as compared with the invention disclosed in U.S. Pat. No. 6,287,079.